JPS62128003A - Method and circuit for erasing recorded data on magnetic recording medium - Google Patents

Abstract

PURPOSE:To erase a desired recorded video part in a very short time while keeping a steady rotation number by impressing an erasing current having the first erasing frequency within the spectrum range of recorded data and erasing recorded data with the second erasing frequency higher than the spectrum range of recorded data. CONSTITUTION:After a recorded video signal is erased for a time T1 by the erasing current having a frequency fER1 within the video signal spectrum range, it is erased furthermore for a time T2 by the erasing current having a frequency fER2 higher than the video signal spectrum. Consequently, a time T required for erasing is T1+T2, and the output of an OR gate is a pulse 63. Through erasing time T1 and T2 with respective frequencies are determined experimentally, sufficiently practical results are attained if T is 1/12-1/6sec. This time T corresponds to 5-10 rotations because the time required for one rotation of a magnetic sheet 1 is 1/60sec.

Description

Detailed Description of the Invention [Field of Industrial Application 1] The present invention generally relates to a method and circuit for erasing recorded data on a magnetic recording medium, and more specifically, to a method and a circuit for erasing recorded data on a magnetic recording medium, and more specifically, to a method and a circuit for erasing recorded data on a magnetic recording medium. The present invention relates to a method and circuit for erasing recorded data.

[Prior Art] In recent years, so-called electronic still cameras have been proposed, which are devices that record still image data on a magnetic sheet-like recording medium (hereinafter referred to as a "magnetic sheet") without using a photosensitive film. In this electronic still camera, one field information is assigned to each of the concentric recording tracks of the disc-shaped magnetic sheet, so that field images for the number of tracks or frame images for half the number of tracks can be recorded.

That is, in a magnetic sheet that generally has 50 tracks,
It can record 50 field images and 25 frame images.

Unlike photosensitive film, magnetic sheets can be erased and rewritten, so in actual use, it is desirable to be able to arbitrarily erase images recorded on the magnetic sheet as specified by the user. For this reason, a dedicated erasing device separate from the electronic still camera has also been proposed.

[Problems to be Solved by the Invention] However, in order to completely erase imaged data so as not to interfere with the next recording, it is preferable to overwrite this data at a higher frequency, but the conventional erasing method In order to increase the erasing frequency, the apparatus lowers the number of rotations of the magnetic sheet than the number of rotations during recording. For example, if the steady rotation speed is 360 Orpm, 1/n of that
Rotation (n = 2.3°4.5...) was selected. Whether you want to erase all the video signals on one magnetic sheet or just a specific video signal, it is necessary to be able to check the recording status on the video. The eraser requires a rotation control system that can switch between steady rotation and low-speed rotation.
Such a rotation control system becomes complicated, and the eraser becomes expensive.

It is also preferable that such an erasing device is built into the electronic still camera itself, but if you want to start shooting immediately after erasing, you can first raise the slow-rotating magnetic sheet to steady rotation and stabilize it. It is necessary to
Since this stabilization takes time, the user feels inconvenienced.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an erasing method and a circuit that can erase a desired recorded video portion within an extremely short time while maintaining the rotational speed at which normal recording is performed, that is, the steady rotational speed.

A second object of the present invention is to provide a compact and simple erase method and circuit that can be integrated into an electronic still camera.

A third object of the present invention is to provide an erasing method and circuit that can perform erasing without providing a dedicated erasing head.

[Means for Solving the Problems] In the erasing method according to the present invention, an erasing current having a first erasing frequency within the spectral range of recorded data is applied to the magnetic head, and - a first step of erasing unnecessary data is performed. and a second step of erasing the magnetic recording at the first erasing frequency at a second erasing frequency higher than the spectral range of the recorded data.

As a result of these two switches, signals within the spectral range of recorded data are completely erased from the magnetic recording medium.

When erasing at the first erasing frequency, it is preferable to gradually lower the applied level.

Further, in the erasing circuit according to the present invention, the first erasing frequency is erased by applying a constant DC voltage during the first erasing period to the input of the FM modulator that performs FM modulation on the luminance signal of the video signal. Create an electric current. This eliminates the need to provide a special oscillator to generate the erase current at the first erase frequency. An amplifier is provided to amplify the erase current at the first erase frequency. Also, for the second cancellation frequency,
A dedicated oscillator is provided, or a switching circuit is provided to shift the oscillation frequency of the FM modulator to a higher side.

[Example] Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. 10
is an analog switch for switching the flow path, and a line 12 of a luminance signal (Y signal) recorded on the electronic sheet is connected to its switching contact 10a. A switching contact 10b of the switch 10 is connected to ground via a DC power supply 14. The common pole 10c of the analog switch 1° is connected to the FM modulator 16. Common pole 1 of analog switch 10
0c is normally electrically connected to the contact 10a.

The output of the FM modulator 16 is connected to a common pole 18c of an analog switch 18 for switching the flow path. The switching contact 18a of the switch 18 is connected to another analog switch 2 for switching the flow path.
The switching contact 18b of the switch 18 is connected via the amplifier 22 to the switching contact 20b of the switch 2°. Common 20 of analog switch 20
c is connected to the video head 26 via the recording amplifier 24. Reference numeral 28 denotes a disc-shaped magnetic sheet for recording video signals, and a motor 30 for rotating this is controlled by a motor drive circuit 32 to rotate at a constant rotation speed and phase of, for example, 36 (10) rpm. .

An erase pulse is sent on line 34 to indicate when the erase mode is selected. Line 34 connects to a monostable multi 36 which generates pulses of pulse width T+. The output pulses of monostable multi 36 switch analog switches 10 and 18. That is, only when the output of the monostable multi 36 is H (high), the common pole 10c of the switch 10 is connected to the switching contact 10b, and the common pole 18c of the switch 18 is connected to the switching contact 18b. The output of monostable multi 36 is also connected directly to one input of OR gate 38 and via a second bistable multi 40 to the other input of OR gate 38 . The second monostable multi 40 generates a pulse with a pulse width T2 in response to the falling edge of the output pulse of the first monostable multi 36.

The output of the OR gate 38 controls the flow path switching of the switch 20. That is, only when the output of the OR gate 38 is H (high), the common pole 20c of the switch 20 becomes the switching contact 20tl.
Connect to.

An oscillator 44 having an oscillation frequency fER2 is connected to the input of the amplifier 220 via a normally open on/off switch 42.

This open/close switch 42 is configured so that the output of the monostable multi 40 is H.
Closed only when (high).

Next, the operation of the circuit disclosed in FIG. 1 will be explained.

In the operation mode in which video signals are recorded on the magnetic seams 1 to 28, the switches 10.18 and 20.42 are in the illustrated state;
The luminance signal on the line 12 is FM modulated by the FM modulator 16, and the sync chip is 6MH7, as shown in FIG.
The white beak has a spectral distribution of 7Mf-1z. This FM-modulated luminance signal passes through switches 18 and 20, is amplified to a predetermined level by a recording amplifier 24, and
Video head 26 records on magnetic sheet 28 .

On the other hand, when the erase mode for erasing the video signal on a desired track on the magnetic sheet 28 is selected, first set the camera to the mF2 number corresponding to the track you want to erase, and then erase the video signal on the track. 2. Position the video head 26 at . After this positioning, a mode selection switch or an erase instruction button (not shown) is operated. Then, the erase pulse 60 shown in the timing chart of FIG.
is supplied on line 34. In response to this erase pulse 60, the monostable multi 36 outputs a pulse 61 with a time width T1.
Output. During this pulse 610 period, switch 10
The common pole 10C of is connected to the switching contact 10b, and the switch 1
The common pole 18c of the switch 20 is connected to the switching contact 18b, and the common pole 20C of the switch 20 is connected to the switching contact 2 by the OR gate 38.
Connect to 0c. In this connection state, the input of the FM modulator 16 is a constant voltage from the DC power supply 14, so its output is at a single frequency f. This becomes the R1 signal. The voltage "ER" of the DC power supply 14 is the same as the frequency of the video signal recorded on the magnetic sheet, for example, 7MH7 of the white peak.
Adjust so that

The output of the single frequency f 1 of the FM modulator 16 is the output of the amplifier 2.
2, the signal is amplified to a sufficient extent for data erasure. Assuming that the normal recording current is 40 to 50+11 A, the amplification degree of the amplifier 22 is set so that the erase current at the subsequent stage of the recording amplifier 24 is 1(10)0 IA or more.

When the pulse 61 ends, in response to the falling edge of the pulse 61, the monostable multi 40 starts the pulse 62 of period T2.
occurs. Upon termination of pulse 61, common pole 10c of switch 10 connects to switching contact 10a, and switch 18
The common pole 18c is connected to the switching contact 18a.

However, since the switch 20 receives the output pulse 62 of the monostable multi 40 via the OR gate 38, the common pole 20C still connects to the switching contact 20b. The output pulse 62 of monostable multi 40 causes switch 42 to close. In this state of switches 10, 18, 20.42, an erase current of oscillation frequency fER2 from oscillator 44 is supplied to video head 26 via amplifier 22 and recording amplifier 24. Note that this oscillation frequency fER□
In this case, a value larger than the FM frequency band of the video signal is selected. For example, it is four times the frequency of the color subcarrier (3.58 MH2) in the NTSC system.

In the present invention, the frequency f□1 within the video signal spectral range
After erasing the recorded video signal over a period T1 with an erasing current of R2, further erasing is performed over a period T2 with an erasing current of a frequency f that is larger than the video signal spectrum. Therefore, the time T required for erasing is T
I +T2, and the output of the OR gate is pulse 63 in FIG. The erasure time T+, T2 at each frequency is
It can be determined experimentally, but T = 1/12 seconds to 1z6
We were able to obtain sufficiently practical results in about seconds. Since the time required for one rotation of the magnetic sheet 28 is 1z60 seconds, this corresponds to 5 to 10 rotations.

After erasing with the erasing current of the first frequency 'ERI, the magnetic sheet has a frequency f
□There is only a signal of 1, but after this, the frequency fER
When erasing is performed with an erase current of 2, the component f decreases and becomes extremely small at the end of T2, as shown in FIG. 4(C).

In order to perform even better erasing, erasing is performed while gradually decreasing the level of the erasing frequency 13 during period T+,
After that, erasing may be performed using the erasing frequency f2. In this way, the residual level of the frequency fF2RI at the end of the period T+ is as shown by the solid line in FIG.
Therefore, erasure by fER2 becomes more effective. This can be achieved, for example, by gradually decreasing the amplification degree of the amplifier 22 during the period T1.

In FIG. 1, if the output of the oscillator 44 is large enough for erasing, the output of the oscillator 44 can be directly
It may be changed so that it is connected to the switching contact 20b of the switch 20. An example of this modification is shown in FIG.

In the configuration of FIG. 2, compared to FIG. 1, instead of the switch 20, the direct output of the FM modulator 16 is amplified by the amplifier 22, and the oscillator 4 of the second cancellation frequency 'ER2 is used.
The difference is that a switch 21 is provided for switching between the output of the monostable multi 40 and the switch 21 is controlled by the output of the monostable multi 40. That is, the common pole 21c of the switch 21 is connected to the recording amplifier 24.
The switching contact 21a is connected to the switching contact 18a of the switch 18 and the output of the amplifier 22, and the switching contact 21a is connected to the switching contact 18a of the switch 18 and the output of the amplifier 22.
1b is connected to the output of the oscillator 44.

The common pole 21c of the switch 21 is connected to the switching contact 21a when the output of the monostable multi 40 is L (low), and is connected to the switching contact 21a (11
When the output of the stable multi 40 is H (high), the switching contact 21
Connect to b.

Since the circuit shown in FIG. 2 is not much different in operation from the circuit shown in FIG. 1, a description thereof will be omitted.

FIG. 3 shows another embodiment of the invention. The same members as the circuit elements in FIG. 1 are given the same reference numerals. In this example,
Oscillator 4 for producing erase current with erase frequency f□2
4, the oscillation frequency of the FM modulator for the luminance signal can be changed. That is, the FM modulator 16 of the luminance signal
A capacitor 72 is connected in series to a capacitor 70 that defines the oscillation frequency of a, and a normally closed short-circuit switch 74 is connected in parallel to the additional capacitor 72. This short circuit switch 74 is in an open state only when the output of the monostable multi 40 is H (high). The OR gate 38a receiving the outputs of the monostable multi 36 and the monostable multi 40 is connected to switch 1.
Controls switching of 0°18.20.

In this embodiment, it is assumed that the FM modulator 16a is a circuit in which the oscillation frequency increases as the capacitance value of the external capacitor 70 decreases. As an example of this kind of FM modulator, we can consider one composed of an emitter-coupled multivibrator. In this case, the oscillation frequency is determined by the external capacitance and the DC voltage applied to the modulator. determined by

In this example, during the period T (=T+ +T2),
The common pole 10c of the switch 10 is connected to the switching contact 10b, the common pole 18c of the switch 18 is connected to the switching contact 18b, and the common pole 20c of the switch 20 is connected to the switching contact 20b. That is, the amplifier 22 is inserted before the recording amplifier 24. Then, only during the period T2, the switch 74
will be released. Therefore, during the period T1, erasing is performed at the first erasing frequency f, similar to the above-described embodiment. Next, during the period T2, the switch 74 is opened, so instead of the capacitance value of the capacitor F alone, the combined capacitance ω value of the series connection of the capacitor 70 and the capacitor 72 is F.
It is involved in determining the oscillation frequency of the M modulator 16a. As mentioned above, the oscillation frequency of this modulator 16a increases as the external capacitance decreases, so the capacitance of the capacitor 72 is determined so that this oscillation frequency is approximately equal to f□2, which exceeds the spectral range of the recorded video signal. put. Then, as in the above-described embodiment, during the period T2, the erasure frequency fo. Deletion is performed.

[Effects of the Invention] As can be seen from the above description, according to the present invention, unnecessary video data can be completely erased without changing the number of rotations of the magnetic sheet.

Further, since a part of the recording circuit is used for erasing, even if the erasing circuit of the present invention is incorporated into an electronic still camera, the volume occupied by the circuit will not increase. Furthermore, 2
Erasing is performed at one frequency, the current value required for erasing at each frequency is small, and circuit design is easy.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the erasing circuit according to the present invention, FIG. 2 is a modified example thereof, FIG. 3 is a block diagram of another embodiment, and FIG. FIG. 5 is a diagram showing a spectral relationship between two erasing currents and a relationship between recording levels on a magnetic sheet, FIG. 5 is a diagram showing a timing chart of two erasing steps, and FIG. The spectrum of 10...Analog switch 12...Brightness signal
14... DC type iii;i 16... FM modulator 18... Analog switch 20... Analog switch 22... Amplifier 24... Recording amplifier 26... Video head 28.・Magnetic sheet
30... Motor 32... Motor drive circuit 34.
...Line 36...Monostable multi 38...○R
Gate 40... Monostable multi 42... Switch 44... Oscillator 60... Erasing pulse 61,6
2.63...Pulse 70...Capacitor 72...
・Capacitor 74... Short circuit switch Fig. 4

Claims (11)

[Claims] (1) A method for erasing data on a desired track of a magnetic recording medium having a plurality of tracks and recording data on each track, the method comprising: positioning a magnetic head on the track of data to be erased; and recording data. erasing unnecessary data by applying an erase current at a first erase frequency within a spectral range of the recorded data to the magnetic head; and a second erase frequency higher than the spectral range of recorded data at the first erase frequency. 1. A method for erasing recorded data on a magnetic recording medium, comprising the step of erasing magnetic recording using a magnetic recording medium. (2) The method according to claim (1), in which the applied level is gradually lowered when erasing at the first erasing frequency. (3) The method according to claim (1) or (2), wherein the recorded data is a video signal. (4) The method according to claim (3), wherein the magnetic recording medium is a magnetic sheet for an electronic still camera. (5) In the first erasing period T_1, a desired data portion of the magnetic recording medium is erased at a first erasing frequency that is within the spectral range of the data recorded on the magnetic recording medium, and in the subsequent second erasing period T_2, A circuit for erasing the data portion at a second erasing frequency that is greater than the spectral range of the recorded data, the circuit comprising: applying a constant DC current to the input of an FM modulator that FM modulates the luminance signal of the video signal during the first erasing period; a changeover switch 10 that applies a voltage; an amplifier that amplifies the output of the FM modulator at the first erasure frequency during the first erasure period T_1; an oscillator that oscillates at the second erasure frequency; During the period T_1, the erase current of the first erase frequency by the amplifier is supplied to the magnetic head excitation current circuit, and during the second erase period T_2, the erase current of the second erase frequency is supplied to the magnetic head excitation current circuit. What is claimed is: 1. A recording data erasing circuit for a magnetic recording medium, comprising: a switching circuit for supplying magnetic head excitation current; and a magnetic head driven by an excitation current from a magnetic head excitation current circuit. (6) The erasing circuit according to claim (5), wherein the magnetic recording medium is a magnetic sheet for an electronic still camera. (7) The switching circuit inputs the output of the oscillator through the amplifier and then into the magnetic head excitation circuit during the second erase period T_2. The erasing circuit described in item (6). (8) The erasing circuit according to any one of claims (5) to (7), wherein the magnetic head is also a signal recording head. (9) In the first erasing period T_1, a desired data portion of the magnetic recording medium is erased at a first erasing frequency within the spectral range of the data recorded on the magnetic recording medium, and in the subsequent second erasing period T_2, A circuit for erasing the data portion at a second erasing frequency that is greater than the spectral range of the recorded data, the circuit comprising: applying a constant DC current to the input of an FM modulator that FM modulates the luminance signal of the video signal during the first erasing period; a changeover switch 10 that applies a voltage; a first changeover circuit that increases the oscillation frequency of the FM modulator to a higher value during the second erasure period T_2; A magnetic recording medium comprising: a second switching circuit that amplifies the output of the modulator and supplies the amplified output to a magnetic head excitation current circuit; and a magnetic head driven by an excitation current from the magnetic head excitation current circuit. Recorded data erasing circuit. (10) The erasing circuit according to claim (9), wherein the magnetic recording medium is a magnetic sheet for an electronic still camera. (11) The erasing circuit according to claim (9) or (10), wherein the magnetic head is also a signal recording head.